This invention relates to lithium ion batteries and electrochemical science, and further relates to boron-doped lithium-rich manganese based cathode materials with its preparation method.
Lithium-ion battery is a kind of secondary battery that can be recharged; it has a 20 year history of development. Its applications include areas such as entertainment, transportation, military, medical treatment, and telecommunications, etc. Recently developed electrical vehicles that employ lithium ion batteries are environmentally friendly and high application prospects, but their popularity is limited for the time being due to the low energy density of the lithium ion batteries. The cathode material is the main factor that limits the energy density of Li ion batteries. Common cathode materials on the market include LiCoO2, LiFePO4, and LiMn2O4, etc., all of which have energy capacity below 200 mA h/g. Thus there is an urgent need to find a cathode material with high energy density.
Lithium rich manganese based material xLi2MnO3. (1-x) LiMO2 (in which M is a combination of Co, Ni, and Mn in a random ratio, e.g. Ni0.5Mn0.5, Ni1/3Mn1/3Co1/3) has attracted the most attention due to its high specific capacity (>250 mA h/g). This material was evolved from Numata's work on composite Li2MnO3.LiCoO2 first proposed in 1999 (Solid state Ionics 1999, 118, 117). The structure of Li-rich manganese based material is still under debate: J. Dahn's (Chem. Mater., 2003, 15, 3214-3220) and J. Ferreira's (Chem. Mater., 2011, 23, 3614-3621) groups believes that it is a solid solution, while Pan's group (Chem. Mater., 2002, 14, 2289-2299) thought it was a pseudo nano composite material instead of a solid solution, whereas Zhou's and Ikuhara's groups consider it as a bi-phase coexisting structure, which is supported by TEM evidence.
Although Li-rich materials have high specific energy capacities, their commercial applications are greatly limited by their short cycle life. Specifically, their capacities rapidly decay to zero after 150 charging-discharging cycles as the result of spinel phase transition, particle fragmentations, and surface corrosions. After 300 charging-discharging cycles, the specific capacity drops to below less than 100 mA h/g, and eventually falls to zero. (ACS Nano, 2013, 7 (1), pp 760-767). Because of these drawbacks, the commercial applications of Li-rich materials are severely limited. There is therefore a need to improve the properties of these materials to improve the materials' performance over a large number of charging-discharging cycles.